Rubbery core/shell polymer with improved heat and UV resistance

Abstract

The present invention relates to rubbery core/shell polymers that have improved heat and ultraviolet light resistance. These polymers can be blended with thermoplastics to make leathery compositions. The core/shell polymers of this invention have an inner core and an outer shell. The inner core is has repeat units which are derived from (a) butyl acrylate, (b) a member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, (c) optionally, an alkoxy ethyl acrylate or an alkoxy ethyl methacrylate, (d) acrylonitrile, (f) a cross-linking agent, and (g) a monomer containing reactive cure sites The outer core has repeat units which are derived from (d) acrylonitrile, (e) styrene, and (f) additional cross-linking agent. The outer core of these polymers is void of repeat units that are derived from methyl methacrylate.

1. A rubbery polymer having improved properties, which is comprised of art inner core and an outer shell, wherein the inner core is comprised of a polymeric structure having repeat units which are derived from a mixture of (a) butyl acrylate, (b) a member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, (c) optionally, an alkoxy ethyl acrylate or an alkoxy ethyl methacrylate, (d) acrylonitrile, (f) a cross-linking agent selected from the group consisting of difunctional acrylates, difunctional methacrylates, trifunctional acrylates, trifunctional methacrylates, divinyl benzene, and 1,4-butanediol dimethacrylate, and (g) a monomer containing reactive cure sites, wherein the reactive cure sites are glycidyl groups, wherein the outer shell is comprised of a polymeric structure having repeat units which are derived from (d) about 4 weight percent to about 30 weight percent acrylonitrile, (e) styrene, and (f) additional cross-linking agent, wherein the outer shell is void of repeat units which are derived from methyl methacrylate. 
     
     
       2. The rubbery polymer as specified in  claim 1  which is comprised of repeat units which are derived from (a) about 40 to about 80% by weight butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to 40% by weight 2-ethylhexyl acrylate, (b) from about 5 to about 35% by weight methyl methacrylate, ethyl methacrylate, methyl acrylate, or ethyl acrylate, (c) optionally, about 0 to about 40% by weight of an alkoxy ethyl acrylate or an alkoxy ethyl methacrylate, (d) from about 4 to about 30% by weight acrylonitrile, (e) from about 3 to about 25% by weight styrene, (f) from about 0.25 to about 8% by weight of a crosslinking agent, and (g) from about 1% to about 10% by weight of the monomer containing reactive cure sites, wherein the outer shell consists of repeat units that are derived from acrylonitrile, styrene, and the additional cross-linking agent. 
     
     
       3. The rubbery polymer as specified in  claim 1  which contains repeat units which are derived from (a) about 50 to about 80% by weight butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 40% by weight 2-ethylhexyl acrylate, (b) from about 3 to about 25% by weight of at least one member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, (c) optionally about 0 to about 40% by weight of an alkoxy ethyl acrylate or an alkoxy ethyl methacrylate, (d) from about 6 to about 30% by weight acrylonitrile, (e) from about 5 to about 18% by weight styrene,(f) from about 0.5 to about 4% by weight of a crosslinking agent, and (g) from about 1% to about 8% by weight of the monomer containing reactive cure sites. 
     
     
       4. The rubbery polymer as specified in  claim 1  which contains repeat units which are derived from (a) from about 55 to about 75% by weight butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 40% by weight 2-ethylhexyl acrylate, (b) from about 5 to about 20% by weight of at least one member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, (c) optionally, about 0 to about 40% by weight of an alkoxy ethyl acrylate or an alkoxy ethyl methacrylate, (d) from about 10 to about 25% by weight acrylonitrile, (e) from about 8 to about 14% by weight styrene, (f) from about 1 to about 3% by weight of a crosslinking agent, and (g) from about 2% to about 6% by weight of the monomer containing reactive cure sites. 
     
     
       5. The rubbery polymer as specified in  claim 1  wherein the monomer containing reactive cure sites is selected from the group consisting of glycidyl methacrylate and allyl glycidyl ether. 
     
     
       6. A leathery composition which is useful in automotive applications wherein the leathery composition is comprised of (1) a thermoplastic, (2) a plasticizer, and (3) the rubbery polymer as specified in  claim 1 . 
     
     
       7. The leathery composition as specified in  claim 6  wherein the thermoplastic resin is polyvinyl chloride. 
     
     
       8. The leathery composition as specified in  claim 6  wherein the thermoplastic resin is a polyolefin. 
     
     
       9. The leathery composition as specified in  claim 8  wherein the polyolefin is high density polyethylene. 
     
     
       10. The leathery composition as specified in  claim 8  wherein the polyolefin is a metallocene catalyzed polyolefin. 
     
     
       11. A process for preparing a rubbery polymer which can be blended with thermoplastics to make leathery compositions having good heat and ultraviolet light resistance, said process comprising the steps of (1) polymerizing a mixture of (a) butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 40% by weight 2-ethylhexyl acrylate, (b) at least one member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, (c) optionally about 0% to about 40% of alkoxy ethyl methacrylate, (d) acrylonitrile, and (e) a crosslinking agent selected from the group consisting of difunctional acrylates, difunctional methacrylates, trifunctional acrylates, trifunctional methacrylates, divinyl benzene, and 1,4-butanediol dimethacrylate; wherein about 1% to about 10% by weight of a monomer containing reactive cure is incorporated into the rubbery polymer under emulsion polymerization conditions to produce a seed polymer containing latex, wherein the monomer containing reactive cure sites contains glycidyl groups; (2) adding a monomer mixture consisting of (a) styrene, (b) additional acrylonitrile, and (c) additional crosslinking agent to the seed polymer containing latex under emulsion polymerization conditions which result in the formation of an emulsion containing the rubbery polymer, wherein no additional methyl methacrylate is added to the seed polymer latex; and (3) recovering the rubbery polymer from the emulsion containing the rubbery polymer. 
     
     
       12. The process as specified in  claim 11  wherein the polymerization is a free radical emulsion polymerization. 
     
     
       13. The process as specified in  claim 12  wherein the polymerization is conducted at a temperature which is within the range of about 10° C. to about 95° C. 
     
     
       14. The process as specified in  claim 13  wherein from about 6 parts by weight to about 22 parts by weight of the styrene, about 3 parts by weight to about 12 parts by weight of the additional acrylonitrile, and about 0.05 parts by weight to about 1 part by weight of the crosslinking agent are added to the seed polymer latex in step (2). 
     
     
       15. The process as specified in  claim 14  wherein the crosslinking agent is 1,4-butanediol dimethacrylate. 
     
     
       16. The process as specified in  claim 15  wherein the polymerization is conducted at a temperature which is within the range of 20° C. to 80° C. 
     
     
       17. The process as specified in  claim 16  wherein from 10 parts by weight to 17 parts by weight of the styrene, 4 parts by weight to 8 parts by weight of the additional acrylonitrile, and 0.1 parts by weight to 0.5 part by weight of the 1,4-butanediol dimethacrylate are added to the seed polymer latex in step (2). 
     
     
       18. A rubbery polymer having improved properties, which is comprised of an inner core and an outer shell, wherein the inner core is comprised of a polymeric structure having repeat units which are derived from a mixture of (a) butyl acrylate, (b) a member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, (c) optionally, an alkoxy ethyl acrylate or an alkoxy ethyl methacrylate, (d) acrylonitrile, (f) a cross-linking agent selected from the group consisting of difunctional acrylates, difunctional methacrylates, trifunctional acrylates, trifunctional methacrylates, divinyl benzene, and 1,4-butanediol dimethacrylate, and (g) a monomer containing reactive cure sites selected from the group consisting of dicyclopentenyl acrylate and dicyclopentenyloxyethyl methacrylate, wherein the outer shell is comprised of a polymeric structure having repeat units which are derived from (d) about 4 weight percent to about 30 weight percent acrylonitrile, (e) styrene, and (f) additional cross-linking agent, wherein the outer core is void of repeat units which are derived from methyl methacrylate. 
     
     
       19. The rubbery polymer specified in  claim 18  wherein the inner core consists of a polymeric structure having repeat units which are derived from (a) butyl acrylate, (b) a member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, (c) optionally, an alkoxy ethyl acrylate or an alkoxy ethyl methacrylate, (d) acrylonitrile, (f) a cross-linking agent selected from the group consisting of difunctional acrylates, difunctional methacrylates, trifunctional acrylates, trifunctional methacrylates, divinyl benzene, and 1,4-butanediol dimethacrylate, and (g) a monomer containing reactive cure sites selected from the group consisting of dicyclopentenyl acrylate and dicyclopentenyloxyethyl methacrylate, and wherein the outer shell consists of a polymeric structure having repeat units which are derived from (d) about 4 weight percent to about 30 weight percent acrylonitrile, (e) styrene, and (f) additional cross-linking agent. 
     
     
       20. The rubbery polymer as specified in  claim 19  which contains repeat units which are derived from (a) about 50 to about 80% by weight butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 40% by weight 2-ethylhexyl acrylate, (b) from about 3 to about 25% by weight of at least one member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, (c) optionally about 0 to about 40% by weight of an alkoxy ethyl acrylate or an alkoxy ethyl methacrylate, (d) from about 6 to about 30% by weight acrylonitrile, (e) from about 5 to about 18% by weight styrene, (f) from about 0.5 to about 4% by weight of a crosslinking agent, and (g) from about 1% to about 8% by weight of the monomer containing reactive cure sites.